450 kilometers/sec near the Earth, but there are low-speed and high-speed streams within this wind that travel 200 to 1000 km/sec. The wind blows with essentially the same speed all the way out to the orbit of Neptune, and it is expected that by a distance of 150 Astronomical units it impacts the interstellar medium and forms a shock front where it suddenly decelerates. This is called the heliopause, and the Voyager and Pioneer spacecraft are expected to reach it in the early part of the next century.
All answers are provided by Dr. Sten Odenwald (Raytheon STX)
NASA IMAGE/POETRY Education and Public Outreach program.